The present invention relates to caliper brake apparatus of the side-pull type for bicycles, and more particularly to a center adjusting device for such brake apparatus.
Brake apparatus of this type are widely used in bicycles. With caliper brake apparatus for bicycles, the shoes attached to the distal ends of opposed brake arms wear away during years of use. Such wear takes place not uniformly but invariably unevenly. Especially in the case of the side-pull type, uneven wear occurs very markedly, producing a difference in the shoe-to-rim clearance between the opposite sides of the wheel rim, with the result that the brake fails to operate properly on one side. This is likely to cause a serious accident.
Accordingly when a difference in the shoe-to-rim clearance occurs between the opposite sides of the wheel, there arises the necessity of properly adjusting the clearance, but the adjustment requires a cumbersome procedure, needs skill and is therefore difficult to make accurately.
To overcome the problem, I proposed a brake apparatus equipped with a center adjusting device, which has already been patented as U.S. Pat. No. 4,263,990 (U.S. Patent Application Ser. No. 21,477). The proposed center adjusting device comrises a fixed member fixedly mounted on a center rod for supporting the brake apparatus, and a turnable member turnably mounted on the center rod and holding a brake spring, such that the distance between the fixed member and the turnable member is adjusted by an adjusting screw member to center the brake apparatus. The screw member is screwed in a nut turnably supported on the turnable member. Accordingly the screw member, when advanced or retracted relative to the nut, alters the distance between the fixed member and the turnable member for centering. At this time, the nut turns relative to the turnable member while moving along the screw member. However, the device has the drawback that if the screw member is advanced or retracted on the nut when the nut is unable to turn due to deposition of dust, soil or sand, the screw thread will be collapsed to render the device no longer operable for center adjustment.